Method of developing electrostatic latent images with pressure sensitive toner

ABSTRACT

A pressure fixable toner comprised of a weakly crosslinked amorphous polymer the crosslink bonds of which are disrupted and/or broken by the application of pressure whereby the polymer is sufficiently soft to be fixed by pressure.

United States Patent 1191 Strella et al.

[ 1 Dec.23, 1975 METHOD OF DEVELOPING ELECTROSTATIC LATENT IMAGES WITHPRESSURE SENSITIVE TONER [75] Inventors: Stephen Strella, Pittsford;Meurig W. Williams, Rochester, both of [73] Assignee: Xerox Corporation,Stamford,

Conn.

22 Filed: Dec.6, 1973 5 [21] Appl. No.: 422,399

[44] Published under the Trial Voluntary Protest Program on January 28,1975 as document no. B 422,399.

Related US. Application Data [62] Division of Ser. No. 214,441, Dec. 30,1971, Pat. No.

[52] US. Cl. 427/22; 96/1 SD; 427/195; 427/19 [51] Int. CL. G03G 7/00;G036 13/00; B44D 1/94 [58] Field of Search 96/1 SD; 117/175, 21;

OTHER PUBLICATIONS T879,009-Staudenmayer, et aL, 4/23/70.

Primary ExaminerN0rman G. Torchin Assistant ExaminerLouis V. FalascoAttorney, Agent, or Firm-James J. Ralabate; Donald C. Kolasch; Ernest F.Chapman 1 1 ABSIRACT A pressure fixable toner comprised of a weaklycrosslinked amorphous polymer the crosslink bonds of which are disruptedand/or broken by the application of pressure whereby the polymer issufficiently soft to be fixed by pressure.

10 Claims, No Drawings METHOD OF DEVELOPING ELECTROSTATIC LATENT IMAGESWITH PRESSURE SENSITIVE TONER This is a division of application Ser. No.2 l4,44l filed Dec. 30, 1971 now US. Pat. No. 3,804,764.

This invention relates to electrostatography, and more particularly toimproved electrostatographic developing materials and the use thereof.

Electrostatography is best exemplified by electrophotography. The basicelectrophotographic process, as taught by C. F. Carlson in US. Pat. No.2,297,691, involves placing a uniform electrostatic charge on aphotoconductive insulating layer, exposing the layer to alight-and-shadow image to dissipate the charge on the areas of the layerexposed to the light and developing the resulting latent electrostaticimage by depositing on the image a finely divided electroscopic materialreferred to in the art as toner. The toner will normally be attracted tothose areas of the layer which retain a charge, thereby forming a tonerimage corresponding to the latent electrostatic image. This powder imagemay then be transferred to a support surface such as paper. Thetransferred image may subsequently be permanently affixed to the supportsurface as by heat. Instead of latent image formation by uniformlycharging the photoconductive layer and then exposing the layer to alight-and-shadow image. one may form the latent image by directlycharging the layer in image configuration. The powder image may be fixedto the photoconductive layer if elimination of the powder image transferstep is desired. Other suitable fixing means such as solvent orovercoating treatment may be substituted for the foregoing heat fixingsteps.

Final copies of the toner image are generally prepared by heating thetoner image on a suitable support to a temperature at which the tonerflows in order to effect fusing of the toner to the support medium. Inorder to increase the speed at which toners may be fixed to a supportattempts have been made to form toners of low molecular weight resinswhich are easily heat fused at relatively low temperatures, but suchattempts have not generally been successful in that such toners tend toblock at low temperatures. Accordingly, there is a need for new tonerswhich can be fixed rapidly, and which have the physical propertiesrequired to withstand the conditions which are employed in thedeveloping process.

An object of this invention is to provide an improvedelectrostatographic developer.

Another object of this invention is to provide a toner which can befixed rapidly and which has the physical properties required towithstand the conditions encountered in the developing process.

A further object of this invention is to provide a toner which iscapable of being fixed to a support surface by the application ofpressure.

These and other objects of the invention should be apparent from readingthe following detailed description thereof.

The objects of this invention are broadly accomplished by providing anelectrostatographic toner of a finely divided colored resinous materialin which the resinous material includes a weakly crosslinked amorphouspolymer having a glass transition temperature (Tg) of greater than aboutC. The crosslinks of the polymer, as a result of their weakness, areshear sensitive and can be temporarily disrupted and/or bro- 2 ken bythe application of pressure, resulting in a polymer which has theproperties of the uncrosslinked poly mer. Upon release of the pressure,the polymer reverts to its crosslinked state. Accordingly, such a toneris capable of being fixed to a support medium in image configuration, bythe application of pressure.

The weakly crosslinked polymer is produced from a polymer having a Tg ofless than 40 C, with the increase in Tg exhibited by the crosslinkedpolymer resulting from the production of the crosslinks. The ton ers ofthe present invention are capable of being fixed to a final copy by theapplication of pressure.

More particularly, the uncrosslinked polymer (commonly referred to as aprepolymer) from which the weakly crosslinked polymer is prepared is anamorphous polymer which has a Tg from about l00 C to about 40 C,preferably from about 50C to about 20 C. It is to be understood,however, that these specified lower Tg limits are only exemplary of thestarting materials employed in that polymers with a Tg lower than l00 Ccan be employed, provided the weakly crosslinked polymer producedtherefrom has the specified Tg. The polymer molecular weight (numberaverage) of the uncrosslinked polymer is generally from about 500 toabout 100,000, preferably from about 1,000 to about 50,000 and includesmore than two crosslink sites per molecule (functionality of molecule isgreater than two) which are reactable to provide crosslinks having abond strength from about 2 to about 30 kcal/- mole, and preferably bondstrengths from about 3 to about 15 kcal/mole. The Tg of the prepolymerand the number of crosslink sites therein are such that, uponcrosslinking, the Tg of the crosslinked polymer is raised to a valuefrom about 20 C to about 50 C, and preferably to a value from about 20 Cto about 50 C. Accordingly, the polymer which is used in preparing thetoners of the present invention is a weakly crosslinked amorphouspolymer having a crosslink bond strength from about 2 to about 30kcal/mole, a Tg from about 20 C to about 50 C.

In providing the weakly crosslinked amorphous polymers which are used inproducing the toners of the present invention to provide a pressurefixable toner. the molecular weight, crosslink bond strength and glasstransition temperature is selected within the specified ranges toprovide a polymer having a yield stress sufficiently low to permityielding by the application of pressure. In general, the weaklycrosslinked amorphous polymers which are suitable for the purposes ofthe present invention have a yield stress from about 500 to about 20,000psi., and preferably a yield stress from about 1,000 to about 5,000 psi.

The weak crosslinks of the polymers which are suitable for the purposesof the present invention are formed by associative bonding (as opposedto covalent bonding), and as representative examples of types ofassociative bonding there may be mentioned; hydrogen bonding; ionicclustering (sometimes referred to as ionic crosslinking with such weaklycrosslinked polymers sometimes being referred to as ionic polymers orionomers, with the term ionic polymer" as used herein referring to suchweakly crosslinked polymers); metal coordinate bonding (including butnot limited to chelates); and weak acid-weak base bonding (including butnot limited to Lewis Acid Bronsted Base bonding).

As representative examples of weakly crosslinked polymers in which thecrosslink is formed by hydrogen bonding there may he mentioned: polymersincluding a carboxylic acid group. phenolic groups, amine groups, amidegroups and the like. As representative examples of specific polymerswhich having hydrogen bonding and are suitable for the purposes of thepresent invention, there may be mentioned; a copolymer of n-butylmethacrylate and acrylic acid; a copolymer of vinyl n-alkyl pyridine andhexylmethacrylate; a copolymer of diacetone acrylamide and butylacrylate; poly (N,N- diisobutylhexamethyleneadipamide) and the like.

As representative examples of weakly crosslinked polymers in which thecrosslink is formed by metal coordinate bonding, there may be mentioned:polymers which include functional groups capable of forming a bond witha metal having a valency greater than one, with such functional groupsgenerally being either a carbonyl group, an ether group, a thio ethergroup, an amino group, an amide group and the like.

Weak acid-weak base associative bonding results from a single polymerwhich includes both acid and base groups or a polymer mixture whichincludes both acid and base groups, with the acidic functionality beingexemplified by one or more of the following groups: carboxylic acids,boric acids, sulfonic acids, phosphonic acids, sulfinic acids and thelike. The basic functionality groups are exemplified by one or more ofthe following groups: hydroxyl, pyridyl, amino and the like. Asrepresentative examples of weakly crosslinked polymers in which theassociative bonding results from weak-acid-weak base bonding there maybe mentioned: vinyl alcohol-vinyl acetate copolymer admixed with boricacid; vinyl pyridine acrylic acid butyl acrylate terpolymer and thelike.

The ionic crosslinkages or clusterings are formed, as known in the art,by the polymer including a negative and/or positively charged groups(s)either pendant to the polymer backbone, incorporated into the polymerbackbone, or terminal to the polymer backbone, which is neutralized byan oppositely charged group to pro vide the ionic crosslink or cluster.

As representative examples of amorphous ionic polymers there may bementioned polymers which include: as negatively charged groups, eitherfree carboxylate groups (COO), free sulfonate groups O S), or phosphategroups, which may be neutralized with a metal cation or an amino cation,etc.; or as a positively charged group, a free amino group, which may beneutralized with either a carboxylate group, an acid halide, inparticular an acid chloride or bromide, a sulfonate group, etc. It is tobe understood that the polymer may be formed with both negatively andpositively charged groups to produce the ionic crosslink or cluster orthe polymer may be formed with either a negatively or positively chargedgroup and subsequently neutralized. It is also to be understood that thenegatively and/or positively charged group may be pendant to the polymerbackbone, incorporated into the polymer backbone or terminal to thepolymer backbone, the aforesaid terminal group being derived either fromthe monomer(s) used in preparing the polymer or subsequently added as aterminal group to the polymer, as known in the art. The followingstructurally illustrates these various ionomer types:

4 e.g., styrene/nbutyl methacrylate/potassium methacrylate.

iroo' a a e.g., n-butyl methacrylate/vinyl n-methylpyridinium acid.

4. Na OOC COO Na* e.g., carboxylic acid terminated n-butylmethacrylatehomopolymer neutralized with sodium. It is to be understood that inpolymers of this type more than two acid groups are associated with eachsodium ion to produce a crosslink network.

e.g., Diamino terminated amorphous polyamide neutralized withhydrochloric acid. it is to be understood that in polymers of this typemore than two amino groups are associated with each chloride ion toproduce a crosslink network.

It is also be understood that a mixture of a polymer containing anegatively charged group and a polymer containing a positively chargedgroup may be employed to provide the ionic crosslink.

The degree of neutralization of the polymer; i.e., the amount of ioniccrosslinking or clustering, affects the glass transition temperature ofthe ionic polymer and the degree of neutralization of the prepolymer iscontrolled to provide an ionic polymer having a glass transitiontemperature, as hereabove described. It is also to be understood thatthe quantity of metal cation employed may also affect the humiditysensitivity and conductivity of the polymer, with an increase in thecation content making the ionic polymer more sensitive to moisture.

The monomers which are used in producing the weakly cross-linkedpolymers of the present invention, and in particular the ionic polymers,may be homopolymerized or copolymerized to provide a polymer having therequired Tg. It is to be understood that monomers which are known tohomopolymerize to polymers having a Tg in excess of those suitable forthe purposes of the present invention may also be employed as comonomersin that by properly selecting the other comonomer(s), as known in theart, a copolymer can be produced with the required Tg; i.e., thecopolymer has a Tg intermediate the Tgs of each of the homopolymersproduced from such polymers and by selecting the monomers and theproportions thereof, a copolymer with the required Tg may be produced.As representative examples of monomers which are suitable for thepurposes of the present invention there may be mentioned: styrenes, suchas styrene, chlorostyrene, amethyl styrene; alkyl methacrylates, whereinthe alkyl groups has 1-3 carbon atoms, such as methyl methacrylate,ethyl methacrylate; aminoalkylmethacrylates wherein the alkyl has 1-6carbon atoms; acrylonitrile; vinyl acetate; vinyl chloride; acrylicacid; methacrylic acid and n-alkyl vinyl pyridinium salt; which arepreferably copolymerized with one or more of the following monomers:alkyl acrylates where the alkyl group contains l-12 C atoms: alkylmethacrylates where the alkyl group contains 4l2 C atoms, e.g., methylacrylate, n-butyl acrylate, 2-ethylhexyl aerylate, n-butyl methacrylate,lauryl methacrylate; vinylidene chloride and the like.

Condensation monomers include dicarboxylic acids, diols, diamines,di-isocyanates, etc. Examples are adipic acid, dimer acid,"commercialized as Empol 1010 (Emerey Industries) or Versadyme (GeneralMills), hexamethylene diamine, dimer diamine and dimer diisocyanate(DDI) commercialized by General Mills, hexanediol, etc., and the like.

As representative examples of polymers which are suitable for thepurposes of the present invention, in particular for the production ofionic polymers, there may be mentioned: poly(ethyl acrylate);styrene/nbutyl methacrylate; styrene/ethyl acrylate;acrylonitrile/n-butyl acrylate; methyl methacrylate/methyl ac rylate;vinyl chloride/methyl acrylate; ethyl methacrylate/vinylidene chloride;n-methyl vinyl pyridinium salt/n-butyl methacrylate; acrylicacid/n-butyl methacrylate; poly-N,N'-diisobutylhexamethylene sebacamide;poly-2,2,4-trimethyl hexamethylene adipate 2,2,4-trimethylhexamethyleneadipamide.

The procedures for preparing such polymers are known in the art, and nodetailed explanation thereof is deemed necessary for a fullunderstanding of the presem invention.

The production of ionic polymers, i.e., the formation of ioniccrosslinks or ionic clusters, is also performed as known in the art,e.g., note US. Pat. No. 3,264,272 which describes neutralizationprocedures for producing ionic crosslinks or clusters. The metal ionswhich are generally employed for producing the ionic crosslinks orclusters are the monodiand trivalent ions of metals in Groups I, ll,[[l, lV-A and VIII of the Periodic Table of Elements (see page 392,Handbook of Chemistry and Physics, Chemical Rubber Publishing Co., 37thed.). Suitable monovalent metal ions are Na", K", Li*, Cs, Ag", Hg andCu". Suitable divalent metal ions are Be, Mg, Ca, Sr, Ba, Cu, Cd, Hg,Sn, Pb, Fe, Co, Ni and Zn. Suitable trivalent metal ions are Al, Sc, Feand Y.

As representative examples of suitable anions for neutralizing cationicgroups, there may be mentioned chloride, bromide, iodide, fluoride,sulfate, nitrate, borofluoride, chromate, chloroplatinate, methanesulfonate, toluene sulfonate, acetate, propionate, etc. These anions areintroduced into the ionomer by neutralizing the basic polymers with thecorresponding acids, hydrochloride, hydrobromic, etc., either insolution or by a milling procedure.

The use of a weakly crosslinked polymer, as hereinabove described, in atoner is advantageous in that such a toner is capable of being pressurefixed and also has the properties desired for storage and use of thetoner; i.e., resistance to impactation and blocking. Although thepresent invention is not limited to any theoretical reasons it isbelieved that the polymer, in its crosslinked state, provides sufficienttoughness to resist impactation and blocking, and upon application ofpressure, which effects disruption or breaking of the crosslinks, thepolymer is sufficiently soft to be deformed and affixed to a suitablesupport member. Upon release of the pressure, the crosslinks arereestablished, and the 6 deformed polymer, in image configuration, isretained on the support medium.

The toner of the present invention includes a colorant, either a pigmentor dye, in a quantity sufficient to impart color to the resincomposition, generally in a quantity up to about 25%, by weight, andparticularly from about l% to about 20%, by weight, of the toner,whereby the resulting toner will form a clear visible image on atransfer member. Any one ofa wide variety of pigments or dyes which donot adversely affect the properties of the toner may be employed toimpart color to the resin; e.g., carbon black, a commercial red, blue oryellow dye, and since such dyes and/or pigments are well-known in theart, no detailed enumeration thereof is deemed necessary for a fullunderstanding of the invention.

The colored toner may be prepared by any one of a wise variety ofprocedures for forming a uniform dispersion of the dye or pigment in theresinous material. Thus, for example, the resinous material and asuitable pigment may be heated and blended on a rubber mill and thenallowed to cool and harden to encase the pigment within the resinousmaterial. The pigmented or dyed resinous material is then micronized;e.g., in a jet pulverizer, to particles having a particle size generallyemployed for a toner; generally an average particle size of less thanabout 30 microns, preferably an average particle size from about 10 toabout 20 microns. Alternatively, the finely divided toner may beprepared by spray drying a toner composition of the colorant and resindissolved in a solvent.

The above procedures and other procedures for producing colored toner ofthe desired particle size are generally known in the art and may beemployed for producing the toner of the present invention and therefore,no detailed discussion thereof is necessary for a full understanding ofthe invention.

The hereinabove described toner of the invention formed from a weaklycrosslinked amorphous polymer may also include other materials generallyemployed for modifying the characteristics of a toner, such asconductive materials to modify the triboelectric properties thereof,magnetic material or the like, and the use of such materials is deemedto be within the scope of those skilled in the art from the teachingsherein. Similarly, the toner may include a resinous component other thanthe hereinabove described weakly crosslinked polymer, provided that atleast a major portion of the resinous portion of the toner is comprisedof the hereinabove described crosslinked polymer; generally thecrosslinked polymer comprises from about to about l()0%, preferably fromto of the resinous portion of the toner. The remaining portion of theresinous component of the toner, if any, is generally a resin of thetype employed to modify the physical properties of a toner material;e.g., a long chain thermoplastic which has little tendency towardagglomeration or cold flow, such as, polyvinyl butyral, polyethyleneshellac, waxes, polyesters, polyvinyl acetal, polyvinyl chloride,polyvinyl acetate and the like.

The toner hereinabove described, is employed in a developer compositionby loosely coating the toner on a suitable electrostatographic developercarrier surface to which the toner is affixed by electrostaticattraction, as generally known in the art. Thus, for example, the tonercomposition may be employed in the cascade development technique, asmore fully described in US. Pat. No. 2,618,551 to Walkup, US. Pat. No.2,618,552

to Wise, and U.S. Pat. No, 2,638,4[6 to Walkup et al. In the cascadedevelopment technique, the developer composition is produced by mixingtoner composition with a carrier, either electrically conducting orinsulating, magnetic or non-magnetic, provided that the carrier materialwhen brought in close contact with the toner composition acquires acharge having an oppo site polarity to that of the toner whereby thetoner adheres to and surrounds the carrier. Thus, the carrier materialis selected in accordance with its triboelectric properties so that thetoner is either above or below the carrier material in the triboelectricseries, to provide a positively or negatively charged toner.

The carrier particles are larger than the toner particles by at leastone order of magnitude of size and are shaped to roll across the latentimage-bearing surface. In general, the carrier particles should be ofsufficient size so that their gravitational or momentum force is greaterthan the force of attraction of the toner particles in the area of theimage-bearing surface where the toner particles are retained, wherebythe carrier will not be retained by the toner particles which areattracted to the image-bearing surface. The carrier particles generallyhave a particle size from about to about 1,000 microns, but it is to beunderstood, that the carrier particles may be of a size other than asparticularly described, provided that the carrier flows easily over theimage-bearing surface, without requiring special means for effectingremoval of the carrier particles from the image-bearing surface.

The degree of contrast or other photographic qualities in the finishedimage many be varied by changing the relative proportions of toner andcarrier material and the choice of optimum proportions is deemed to bewithin the scope of those skilled in the art. In general, however, thetoner of the invention is employed in amounts to provide weight ratiosof carrier to toner of from about 25:1 to about 250:], preferably fromabout 75:l to about 100:1, to produce a dense readily transferableimage.

In addition to the use of particles to provide the carrier surface, thebristles of a fur brush may also be used. Here also, the toner particlesacquire an electrostatic charge of polarity determined by the relativeposition of the toner particles and the fur fibers in the triboelectricseries. The toner particles form a coating on the bristles of the furclinging thereto by reason of the electrostatic attraction between thetoner and the fur just as the toner clings to the surface of the carrierparticles. The general process of fur brush develop ment is described ingreater detail in US. Pat. No. 3,251,706 to L. E. Walkup.

Even more closely related to the cascade carrier development is magneticbrush development. In this process. a carrier is selected havingferromagnetic properties and selected relative to the toner in a triboelectric series so as to impart the desired electrostatic polarity tothe toner and carrier as in cascade carrier development. On inserting amagnet into such a mixture of toner and magnetic material the carrierparticles align themselves along the lines of force of the magnet toassume a brush-like array. The toner particles are electrostaticallycoated on the surface of the powder carrier particles. Developmentproceeds as in regular cascade carrier development on moving the magnetover the surface bearing the electrostatic image so that the bristles"of the magnetic brush contact the electrostatic image-bearing surface.

Still another method of carrier development is known as sheet carrierdevelopment in which the toner particles are placed on a sheet as ofpaper, plastic, or metal. This process is described in US. Pat. No.2,895,847 to C. R. Mayo. As described therein the electrostaticattraction between the sheet surface and toner particles necessary toassure electrostatic attraction therebetween may be obtained by leadingthe sheet through a mass of electroscopic toner particles whereby thereis obtained a rubbing or sliding contact between the sheet and thetoner. In general, it is desirable to spray the surface of the sheetbearing the electroscopic toner particles with ions of the describedpolarity as by the use of a corona charging device as described in thepatent of Mayo.

The resulting image of toner particles of the imagebearing surface maythen be transferred to a suitable transfer member to form the finalcopy. The transfer of the toner particles may be elTected adhesively orelectrostatically as known in the art.

The toner as should be apparent from the hereinabove teachings, may beemployed in a wide variety of developer compositions byelectrostatically coating the toner composition to a suitable carriersurface, which is subsequently passed over a latent image-bearingsurface. The toner of the invention may be employed for developing anelectrostatic latent image formed by other than electrophotographicmeans; for example, the development of electrostatic latent imagesformed by pulsing electrodes as employed in electrostatic printingprocesses. In addition, the toner of the invention may be employed fordeveloping an electrostatic latent image on a surface other than aphotoconductive insulating surface. Therefore, the overall invention isnot limited to a specific technique for forming or developing anelectrostatic latent image or to a specific carrier for the toner.

The toners of the present invention are capable of being fixed to asuitable support medium such as paper to provide a finished copy by theapplication of pressure; with the particular pressure required foreffecting such pressure fixing varying with the particular toneremployed. The pressure is preferably provided by pressing the transfermaterial having the toner image thereon between a pair of polished metalrollers that are in contact with each other under a specified pressure.In general, the roll loading is from about 10 to about 600 pounds perlinear inch, and preferably from about 50 to about 400 pounds per linearinch. The roll loading in pounds per linear inch is the total appliedforce divided by the length of the roll. In some cases, the pressurefixing of the toner to the support medium may be heat asserted; e.g., bythe use of a coated or uncoated heated metal roll and an uncoated orclastomeric coated backup roll.

It is to be understood, however, that although the toners of the presentinvenion are particularly suitable for the preparation of a final copyby pressure fixing, such toners may also be fixed by conventionalprocedures; e.g., heat fusingv This invention is further illustrated bythe following examples but it is to be understood that the scope of theinvention is not to be limited thereby. Unless otherwise specified, allparts are by weight.

EXAMPLE I Styrene (l0 lb), n-butyl methacrylate (30 lb) and benzoylperoxide are added to a mixture of water 9 lb) including tricalciumphosphate 1.0 lb) and ALKA- NOL B (7.26 g) as emulsifying agent. Themixture is maintained at 90 C for 6 hours and cooled to roomtemperature. 750 ml of concentrated hydrochloric acid is then added todissolve the tricalcium phosphate. After agitating for 20 minutes, themixture is washed with water and dried in air.

The styrene-n-butyl methacrylate copolymer has a styrene content ofabout 35 mole a number average molecular weight of about 44,000 and a Tgof 40 C.

The copolymer is dissolved in boiling isopropanol (l2 gal) and potassiumhydroxide (4.0 lb) added thereto while maintaining reflux. After 2hours, the mixture is precipitated into a large excess of water and theresulting ionic polymer is washed serveral times in water and dried at90 C.

The ionic polymer has a Tg of 48 C and 5.] mole potassium ions.

PREPARATION OF TONER The ionic polymer 19 parts) is dissolved in tetrahydrofuran 100 parts) and mixed with l part MOGUL L carbon black. Thesolvent is evaporated with stirring and vinal traces removed in vacuumoven at 80 C.

The slab of ionic polymer is then ball milled in a polyethylene jarcontaining cylindrical stones for four hours and sieved through a 44 ptgrid. The number average particle size is 9.0.

PREPARATION AND USE OF DEVELOPER The toner is combined with an uncoatedglass bead carrier (the glass is comprised of 42.0% PbO; 18.3% TiO 5.6%BaO; 2.3% ZrO and 3l.8% SiO all by weight) to produce a developer having1 wt of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2inches/sec.

The fixed image is qualitative (removal of the image requires rubbingfor 45 seconds with moderate pressure).

EXAMPLE I] N-butyl methacrylate (950 ml), acrylic acid (50 ml) andazo-bis (isobutyronitrile) g) is dissolved in 2.5 l. acetone andrefluxed for 15 hours. The solution is concentrated to 50% of its volumeand the polymer recovered by precipitation with methanol, followed byextraction with methanol and waterv The polymer is filtered and dried at60 C. The resulting polymer has an acrylic acid content of 5.8 mole Thepolymer is then formed into a toner as described in Example I.

The toner is combined as described in Example I with an uncoated glasscarrier and used to develop an electrostatic latent image as describedin Example I and fixed to paper as described in Example I.

The fixed image is qualitative.

EXAMPLE lll An n-butyl methacrylate vinyl N-methyl pyridine copolymer(94/4) prepared by solution polymerization in acetone using azo-bis(isobutyronitrile) initiator is 10 formed into an ionic polymer byneutralization with a solution of methane sulfonic acid.

The ionic polymer is formed into a toner, used to develop anelectrostatic latent image and fixed to paper as described in Example 1.

The fixed image is qualitative.

EXAMPLE lV An ionic polymer comprised of n-butyl methacrylate, dimethylaminoethyl methacrylate and acrylic acid (94/3/3) is prepared byterpolymerization in acetone solution using azo-bis (isbutyronitrile)initiator.

The ionic polymer is formed into a toner, used to develop anelectrostatic latent image and fixed to paper as described in Example I.

The fixed image is qualitative.

EXAMPLE V 2,2,4-trimethyl hexamethyleneadipamide is prepared by solutionpolymerization using l0 parts of diamine and 9 parts of the adipic acidas described in Condensation Polymers by lnterfacial and SolutionMethods," P. W. Morgan, lnterscience 1965, using an excess of amine foramine termination. An ionic polymer is prepared by neutralization withhydrochloric acid.

A toner is prepared from the ionic polymer as described in Example I.

The fixed image is qualitative.

EXAMPLE Vl Diacetone acrylamide (5 g), n-butyl acrylate (95 g), acetone(300 ml) and azo-bis (isobutyronitrile) (2.0 g) is refluxed overnight,precipitated into methanol, reprecipitated in acetone into methanol anddried in a vacuum over at 60 C.

The resulting polymer (20 g) is dissolved in 50 ml acetone with l gMOGUL L carbon black, evaporated to dryness with stirring and dried in avacuum oven at 60 C. The resulting product is ball milled to produce apulverized material which passes through a 44 p. grid.

The resulting toner is used to develop an electrostatic latent image andfixed to paper is described in Example I.

The fixed image is qualitative.

EXAMPLE Vll Polyvinyl acetate polyvinyl alcohol (l0 mole 7() is preparedby partial hydrolysis of polyvinyl acetate.

The polymer (50 g) is mill rolled with 5 g carbon black and 5 g ofsodium metaborate at C to produce a uniform mixture.

The resulting product is jet micronized with dry ice to an averageparticle size of about l0 microns.

The developer is employed to develop an electrostatic latent image andfixed to paper as described in Example I.

The fixed image is qualitative.

EXAMPLE VIII The nbutyl methacrylate acrylic acid copolymer which isproduced in Example ll is neutralized with potassium hydroxide inmethanol to produce an ionic polymer with 1.4 mole potassium ions (Tg 46C).

The ionic polymer is formed into a toner, used to develop anelectrostatic latent image and fixed to paper as described in Example I.

The fixed image is qualitative.

The toners of the present invention are particularly advantageous inthat such toners are capable of being fixed to a support in imageconfiguration by the application of pressure, and in addition, possessthe structural properties required to withstand the forces encounteredin the development process. The ability to fix a toner image by theapplication of pressure is advantageous in that pressure fixing, withand without heat assistance, is capable of producing fixed images inshorter periods of time.

Numerous modifications and variations of the present invention arepossible in light of the above teachings and, accordingly, within thescope of the appended claims the invention may be practiced other thanas particularly described.

What is claimed is:

l. A process for producing a final toner image comprising:

fixing a toner in image configuration to a support by the application ofpressure, said toner comprising a finely divided colored resin, saidresin comprising an amorphous weakly crosslinked polymer having a bondstrength from about 2 to about 30 kcal/- mole and a Tg of greater thanabout C.

2. A process for rendering an electrostatic latent image visible,comprising:

developing the electrostatic latent image with a finely divided coloredresin, said resin comprising an amorphous weakly crosslinked polymerhaving a crosslink bond strength from about 2 to about kcal/mole and aTg of greater than about -20 C.

3. An electrostatographic development method comprising forming anelectrostatographic latent image on a surface; developing the latentimage with a finely divided electrostatographic toner capable of beingfixed to a support medium in image configuration by the application ofpressure, said toner comprising a finely divided colored resin, saidresin comprising an amphorous weakly crosslinked polymer having acrosslink bond strength from about 2 to about 30 kcal/mole and a glasstransition temperature greater than about 20 C., said weakly crosslinkedpolymer being pressure sensitive; and subjecting the developed imagepresent on the surface to pressure, whereby the pressure application tosaid weakly crosslinked polymer results in a polymer having theproperties of the uncrosslinked polymer thereby fixing said toner tosaid surface.

4. The method of claim 3 wherein the surface is a photoconductiveinsulating surface.

5. The method of claim 4 further comprising transferring the developedlatent image to a suitable transfer member.

6. The method of claim 5 wherein the suitable transfer member is paper.

7. The method of claim 3 wherein the developed image present on thesurface is subjected to pressure by pressing the surface having thetoner image thereon between a pair of polished metal rollers that are incontact with each other.

8. The method of claim 7 wherein the pressure is from about 10 to about600 pounds per linear inch.

9. The method of claim 7 wherein the pressure is from about 50 to about400 pounds per linear inch.

10. The method of claim 3 further comprising applying heat to assist thepressure fixing of the toner.

1. A PROCESS FOR PRODUCING A FINAL IMAGE COMPRISING: FIXING A TONER INIMAGE CONFIGURATION TO A SUPPORT BY THE APPLICATION OF PRESSURE, SAIDTONER COMPRISNG A FINELY DIVIDED COLORED RESIN, SAID RESIN COMPRISING ANAMORPHOUS WEAKLY CROSSLINKED POLYMER HAVING A BOND STRENGTH FROM ABOUT 2TO ABOUT 30 KCAL/MOLE AND A TG OF GREATER THAN ABOUT -20*C.
 2. A PROCESSFOR RENDERING AN ELECTROSTATIC LATEN IMAGE VISIBLE, COMPRISING:DEVELOPING THE ELECTROSTATIC LATENT IMAGE WITH A FINELY DIVIDED COLOREDRESIN, SAID RESIN COMPRISING AN AMORPHOUS WEAKLY CROSSLINKED POLYMERHAVING A CROSSLINK BOND STRENGTH FROM ABOUT 2 TO ABOUT 30 KCAL/MOLE ANDA TG OF GREATER THAN ABOUT -20*C.
 3. An electrostatographic developmentmethod comprising forming an electrostatographic latent image on asurface; developing the latent image with a finely dividedelectrostatographic toner capable of being fixed to a support medium inimage configuration by the application of pressure, said tonercomprising a finely divided colored resin, said resin comprising anamphorous weakly crosslinked polymer having a crosslink bond strengthfrom about 2 to about 30 kcal/mole and a glass transition temperaturegreater than about -20* C., said weakly crosslinked polymer beingpressure sensitive; and subjecting the developed image present on thesurface to pressure, whereby the pressure application to said weaklycrosslinked polymer results in a polymer having the properties of theuncrosslinked polymer thereby fixing said toner to said surface.
 4. Themethod of claim 3 wherein the surface is a photoconductive insulatingsurface.
 5. The method of claim 4 further comprising transferring thedeveloped latent image to a suitable transfer member.
 6. The method ofclaim 5 wherein the suitable transfer member is paper.
 7. The method ofclaim 3 wherein the developed image present on the surface is subjectedto pressure by pressing the surface having the toner image thereonbetween a pair of polished metal rollers that are in contact with eachother.
 8. The method of claim 7 wherein the pressure is from about 10 toabout 600 pounds per linear inch.
 9. The method of claim 7 wherein thepressure is from about 50 to about 400 pounds per linear inch.
 10. Themethod of claim 3 further comprising applying heat to assist thepressure fixing of the toner.